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The method ... is not applicable for the arguments () [duplicate]

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the method in type not applicable for the arguments
(4 answers)
Closed 4 months ago.
I'm trying to complete this code where I need to calculate the density using the mass/volume the user inputs. I have to use two different methods, and call the second method, but when I try to it says, "The method calculateDensity(double[], double[]) in the type Density is not applicable for the arguments ()" W
What's causing the error? This is my code:
import java.util.Scanner;
public class Density {
public static void main(String[] args) {
System.out.println("Enter the mass and volume for your 3 compounds.");
for(int i = 0; i < 3; i++) {
Scanner s = new Scanner(System.in);
double[] volume= new double[3];
volume [i]=s.nextDouble(); // registers user input for volume
} //end for loop
calculateDensity();
} // end main
public static void calculateDensity(double[] mass, double[] volume) {
//
} // end calculate density
} // end class

This is because you are not calling the function with your variables. You need to write calculateDensity(mass, volume);. Otherwise, how would the computer know that you want to pass these two variables to the function? It doesn't work with the same names of the variables and the function arguments.
The variables massand volume are not visible in the scope of the calculateDensity() function, because they are not defined globally.

You need to pass the correct arguments to the calculateDensity method:
calculateDensity(mass, volume);
calculateDensity is a separate method and it needs to receive the mass and volume in order to be able to calculate the density.

you should call your method calculateDensity() whith the aruments as declared, mass and volume.
There are multiple other bugs in your code, this is really basic stuff so maybe figure some out yourself. Hope this doesn't sound too condescensing: we all have started out at one point and made all these mistakes, but getting someone on SO to solve all the problems for you is not the ultimate way to success.

Issue with using array in a class Java

I am trying to build a Java program based on this UML:
UML of Polygon Class
But I ran into a few hiccups along the way. This is my basic code:
import java.util.Scanner;
public class Polygon {
private int[] side;
private double perimeter;
public double addSide(double length[]) {
int i = 0;
double perimeter = 0;
while(length[i] > 0){
perimeter += (double)length[i];
i++;
}
return perimeter;
}
public int[] getSides() {return side;}
public double getPerimeter() {return perimeter;}
public static void main(String[] args) {
Polygon polygon=new Polygon();
polygon.side = new int[99];
int i=0;
do{
System.out.print("Side length(0 when done): ");
Scanner in = new Scanner(System.in);
polygon.side[i] = in.nextInt();
i++;
}while(polygon.side[i]>0);
//polygon.perimeter = addSide((double)polygon.side);
System.out.println("Perimeter of " + i + "-sided polygon: " + polygon.getPerimeter());
}
}
There's a couple of issues.
I got it to compile but when it accepts the first side[0], it immediately stops and gives me the perimeter. Exiting the loop eventhough the conditions haven't been met for it to so. So there's an issue with my while-loop. I want it to keep accepting values into the side[] array until a non-positive value is entered.
Also the UML requires I use double parameter-type for the addSide method. I tried to cast it in the argument and tried a couple of other different things with no success. How would one transition an int-array into a double-array for the perimeter calucalation which has to be double as per the requirements.
I wouldn't surprised if I made other issues since I'm new to Java so feel free to point them out to me or if you have a better way to go about this, I would love to learn your thinking.
Any advice is appreciated!

There are a number of issues with your code.
First, differences from the UML specification:
You haven't used the given signature for addSide. The UML says that it takes a single double parameter, and returns nothing, i.e. void in Java. You are passing an array of double and returning a double.
You are directly accessing sides in your main method. Java allows you to do this, because your main method is part of the Polygon class, but the UML shows that the field is private. What does direct manipulation of sides do to the validity of the value in perimeter?
The UML shows the class having a field sides of type int. Your field sides is of type int[].
Similarly you haven't used the given signature for getSides, which should probably have been named getNumberOfSides.
Your code has quite a few other issues, but I think you should fix the issues above first.
A futher hint: The only things that the Polygon class can do is to tell you how many sides it has and what its total perimeter is. It does not care about the details of individual sides.
(Off topic, it is strange to include main in the UML description of Polygon)

Generate multiple draws (calls) of a given method in java (simulated lottery)

I received the task of simulating a lottery draw in java. The program skeleton yields the method generateOneDraw, which creates 6 random numbers between 1 and 49
static int[] generateOneDraw() {
int numbers[] = new int[NUMBER_OF_ELEMENT_PER_DRAW];
for(int i=0; i<numbers.length; ++i) {
int nextNumber;
do {
nextNumber = generateNextRandomNumber();
} while(numberIsInArray(nextNumber, numbers));
numbers[i] = nextNumber;
}
return numbers;
}
We are then required to implement a function that simulates the lottery draw over 5 weeks and stores them in the variable draws. I believe this should be done over a two-dimensional array. Am I right in this way of thinking? Any pointers on implementing it would be greatly appreciated.
static void generateAllDraws()
Thanks in advance.
EDIT: Nevermind, I did it with a simple two dimensional array and it worked.

Since this seems like home work, I will not go into much detail but you can either:
Create a 2 dimensional list, as per your initial reasoning;
Create a Draw class which represents a lotto draw, and create multiple instances of this class. Each Draw class could have a Date which would denote when did the draw take place.
Both approaches should work, the second approach is a little more object oriented.

How do I make two classes to work together in Java? [closed]

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Closed 9 years ago.
I have been trying for weeks in this project where I have to make one class that generates 500 random numbers from 1-250 and in a second class I have to inherit the first class properties and write all those numbers in a text file but when I have being having problems getting the properties and work with it and I haven't found a way to do it online.
My First class is
import java.util.Random;
public class GenKeys {
public static void random(){
for (int i = 0; i < 250; i++) {
int x = (int) (Math.random() * 100);
}
}
}
and my second code is
import java.util.Random;
import java.io.*;
import java.lang.*;
public class MainProg extends GenKeys{
public static void main(String[] args){
public static void random(){
try {
BufferedWriter out = new BufferedWriter(new FileWriter("file.txt"));
out.write( x + System.getProperty("line.separator"));// when i compile the x is not found!!!
out.close();
} catch (IOException e) {
System.out.print(e);
}
}
How can I make the two classes work together?

What am i doing Wrong ?
You are using inheritance instead of just using an instance of GenKeys in MainProg
You keep overwriting your random values, since you only use a single variable x, when you should be using e.g. an array
You create 250 values in range [0..99] instead of 500 values in range [1..250]
You don't store or return anything from your random() method

and i havent found a way to do it online.
I'm not sure you've looked hard enough.
How to get your code working
Firstly, you want to change the type and name of your method to an int.
public static int randomNum()
Then, remove the loop from the code, and just return the random number generated:
return (int)Math.Random() * 100; //By the way there is a Random class.
In the random method, you want the loop:
for(int x = 0; x < 250; x++)
{
BufferedWriter out = new BufferedWriter(new FileWriter("file.txt"));
out.write( randomNum() + System.getProperty("line.separator"));
}
out.close();
The various issues with your code
You're mis-using inheritance here. Your class is not a type of GenKey. It simply uses it, so it should be a field in your class.
Secondly, a method can only return one value, or one object. It can not return 250 numbers as is. You're assigning 250 numbers to x. This is only going to store the last number generated.

I don't think this is right approach. you need another class, for example KeyWriter to inherit from GenKeys. let it use GenKeys method random (it doesn't need to be static)
also, your random method is wrong, you only generate 250 keys instead of 500, and they are not from 0 to 250.
my solution is:
1) inherit KeyWriter from GenKeys
2) modify random to return only 1 generated number using nextInt
3) use cycle inside KeyWriter to call random 500 times and write those values into a file
4) use KeyWriter class inside you main method
I don't post the actual solution, cause it looks like you're doing your homework.

Well, somethings aren't correct here, but the weirdest of all is that you made the random() function a void.
void random()
Where X goes to? You just create a new int, but do nothing about it.
Besides this, there are other problems, as other folks mentioned around.
I'd recommend you to read about function in Java, especially about the difference between int and void.

Some problems (and comments) I see of the bat:
x is not an instance field and is not stored anywhere thus how can it be accessible from the child class.
Like others have said x is being overwritten with each iteration of your for loop.
Why is the mainProg.random() method declared inside of the mainProg.main() method?
I dont think inheritance is the way to go unless it is absolutely required for this project. Why not just make an instance of your random class inside the main method of the mainProg class?
If you want to use inheritance I believe a call to super.random() will be necessary inside of the mainProg.random() method.(Please someone confirm this. Im not 100% sure)
If it was me I would do something along the lines of this in my GenKeys.random() method:
public int[] random() {
int[] keys = new int[500];
for(int i = 0; i < 500; ++i)
{
keys[i] = (int) (Math.random() * 100);
}
return keys;
}
This code creates and returns an array of 500 keys. NOT in the range of 1-250. See here for that: How do I generate random integers within a specific range in Java?
Hopefully that will get you started on the right track.

x is the local variable of random().
so you can't directly access local variable out side the class.
And you are trying to generate 500 random no. between 1-250 so change the for loop in first class
for (int i = 0; i < 500; i++){
.....
}

Random number generator method for linked list assignment

So, I have to make a random number generator to get numbers ranging from 0 to 400. I'm putting these into an array and then sorting them later on. I just am not sure how to go about doing this. I was given something along the lines of;
public int nextInt(400) //gives me errors
{
random.setSeed(12345L);
for (int i = 0; i < arr.size; i++)
{
val = random.nextInt(400);
a[i] = val;
}
}
I've already called the random class, since the directions indicated that. I just don't know why this is not working. It's giving me errors especially with the first part; class, interface, or enum expected. Could somebody steer me in the right direction please?

Functions in Java (all programming languages) have "variables" in their definition.
You've got:
public int nextInt(400)
Over here, you want your 400 to be a value that is passed to the function.
Think of this as math. I'm sure you've dealt with something like f(x) = 2 * x. Here, x is the variable, and you "evaluate" f(x) with a value for x. Similarly, in programming, we'd have something like :
public int nextInt(int x)
As you see, our function defines x to be of type int. This is necessary in a language like Java because you're telling the compiler that this function will only accept integers for x.
Now that you've done that, you can use x as a variable in the body of your function.
Note that whenever you use a variable, it first has to be defined. A line such as:
int variable;
defines variable as an int.
Your program is missing these for random, val, arr, and a. Note here that arr and a are arrays (and somehow I get the feeling that they should not be two separate variables).
You should really brush up on variables definitions, arrays, and functions before attempting this question. Your best resource would be your textbook, because it'll explain everything in an organized, step-by-step manner. You can also try the many tutorials that are available online. If you have specific questions, you can always come back to StackOverflow and I'm sure you'll find help here.
Good luck!

You need to define this function within a class definition

even you have specified :
public int nextInt(400)
in this line function returns int and in your whole body u didn't have any return statement.
and yes as Kshitij Mehata suggested dont use 400 directly as value use variable over there.
this should be your function:
public int[] nextInt(int x) //gives me errors
{
random.setSeed(12345L);
int[] a=new int[arr.size];
for (int i = 0; i < arr.size; i++)
{
val = random.nextInt(400);
a[i] = val;
}
return a;
}
even there is some issue with arr from where this arr come?